SQLite common function integration

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SQLite date 、 Time Comparison method

SQLite Prompt error ：SQLite error near “@table“: syntax error

SQL Create table ,ID Set up key, And self increase

SQLite Query maximum , Returns the entire line of data

SQLite Add index

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SQLite date 、 Time Comparison method

One 、 new table

The following software is Navicat 15 for SQLite

Create a new table for testing test, Add two fields ,id,myTimer,myTimer Format for datetimer

Two 、 insert data

Query the current time

SELECT DATETIME('now','localtime')

result ：

Know how to get the current time , We ask test Insert data into the table

INSERT INTO test(myTimer) VALUES(DATETIME('now','localtime'))

Randomly generate a few pieces of data , For the following query , as follows ：

3、 ... and 、 Compare time

1. The query is greater than  2022-02-22 16:45:59 The data of

SELECT * FROM test WHERE myTimer > '2022-02-22 16:45:59'

function ：

You can see , The query result is right .

occasionally , It should be noted that , use Where The following query conditions are used “2022-02-22 12:00:00” This format is used for comparison , There will be exceptions , The results are all messy , Completely with Where The condition in does not meet , You can check my post ： Click the jump

stay C# When the time is displayed on the , You can use the following format :

DateTime.Value.ToString("yyyy-MM-dd HH:mm:ss"));

The display is the same as the above

SQLite Prompt error ：SQLite error near “@table“: syntax error

I wrote it before C# operation SQLite In the post , I found that sometimes the following errors occur during operation ：

SQLite error near "@table": syntax error

The error code is as follows ：

public static Tuple<bool, DataSet, string> GetBarcode(string barcode)
{
    if (string.IsNullOrEmpty(barcode))
    {
        return new Tuple<bool, DataSet, string>(false, null, " The passed parameter cannot be empty ");
    }

    string sql = "SELECT * FROM @table WHERE Barcode = @barcode";
    SQLiteParameter[] parameter = new SQLiteParameter[]
    {
        new SQLiteParameter("table", " Database table name "),
        new SQLiteParameter("barcode", barcode)
    };
    return SQLiteHelpers.ExecuteDataSet(sql, parameter);
}

SQLiteHelpers See my previous post for my script ： Click the jump

resolvent ：

I find , Database table name cannot be added to  SQLiteParameter In the parameter list , Other column names are OK ,SQL The statement will not report an error if it is connected by string , as follows ：

public static Tuple<bool, DataSet, string> GetBarcode(string barcode)
{
    if (string.IsNullOrEmpty(barcode))
    {
        return new Tuple<bool, DataSet, string>(false, null, " The passed parameter cannot be empty ");
    }

    string sql = string.Format("SELECT * FROM {0} WHERE Barcode = @barcode", " Database table name ");
    SQLiteParameter[] parameter = new SQLiteParameter[]
    {
        new SQLiteParameter("barcode", barcode)
    };
    return SQLiteHelpers.ExecuteDataSet(sql, parameter);
}

SQL Create table ,ID Set up key, And self increase

sql The statement is as follows ：

CREATE TABLE user
(
	ID 				integer 	PRIMARY KEY AUTOINCREMENT, 
    UserName        text        NOT NULL,
    Age             int         NOT NULL
)

SQLite Query maximum , Returns the entire line of data

Query maximum

SELECT MAX( Name ) FROM  Table name 

Query maximum , Returns the entire line of data

SELECT * FROM  Table name  WHERE  Name = (SELECT MAX( Name ) FROM  Table name ) LIMIT 1;

SQLite Add index

  open SQLite Studio, Create a new table student, Add a few fields ：id、name、age、address

Click on Create index

The following interface will be opened

Sort( Sort )

ASC Expressing ascending order

DESC Representation of descending order

Here in the collation

Collation（ Sort rule ）

RTRIM      Clear the space character at the end of the string

NOCASE     Disable case sensitivity

BINARY     Binary system

SQL sentence ：

example 1 

CREATE INDEX findName ON student (
	name COLLATE BINARY ASC
);

COLLATE It's sort rules

example 2

CREATE INDEX findTestTime ON sampleRecord (
	TestTime ASC
);

findTestTime Is the index name ,

sampleRecord Is the name of the table ,

TestTime Field name ,

ASC Represents ascending order

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